350/th350 to 454/th400 swap

[schulerboy]

Hello, I am seeking some advice regarding swapping the 350/th350 to a 454/th400. My truck is a 75 gmc 1/2ton 2 wheel drive with a 1 piece driveshaft and the doner is a74 3/4ton 2 wheel drive with a 2 piece driveshaft. The tranny mounts look a little different but my main concern is what to do with the driveshaft. What is easier and the best way to go?

[bigchevyc30]

really you wouldnt know due to we dont know the classification of the trucks are they 4door, 2door, short bed, standard bed, or long bed. i know i couldnt help with the final answer but this will help others that do know

[Irish_Alley]

if they are both the same length as stated take the cross member out of the 3/4 and put it in yours and then use the driveshaft. if not the same length get your 1 piece cut down or the 2 piece cut down. its cheaper and easier to cut one down then to lengthen it

[schulerboy]

Both trucks are regular cab long boxes. One concern I have in using the two piece shaft is the center carrier bearing. The bracket it mounts to on the 3/4 ton I don't think I can swap into the 1/2 ton. Would it be easier to just fabricate a new mount for it or is there another bolt in bracket from another year?

[Irish_Alley]

it should fit but if not i have used just a piece of 4" channel before and bolted it to the cross member

[Senck243]

Go to your local driveline shop and get a price on a custom shaft the are around 200-300$.

[Irish_Alley]

yeah only a couple bucks lol. but you can rig one up and work fine. i know i measured a 1/2ton frame and a 3/4 ton both where the same. can this be said for all no but i know the two i measured where the same

[bobcooter]

You could go to a drive line shop and have your 1 piece shortened and balanced for around $100.00